A small count data set. During WWII V1 flying-bombs were fired from sites in France (Pas-de-Calais) and Dutch coasts towards London. The number of hits per square grid around London were recorded.
A data frame with the following variables.
Values between 0 and 4, and 7. Actually, the 7 is really imputed from the paper (it was recorded as "5 and over").
Observed frequency, i.e., the number of grids with that many hits.
The data concerns 576 square grids each of 0.25 square kms about south London. The area was selected comprising 144 square kms over which the basic probability function of the distribution was very nearly constant. V1s, which were one type of flying-bomb, were a “Vergeltungswaffen” or vengeance weapon fired during the summer of 1944 at London. The V1s were informally called Buzz Bombs or Doodlebugs, and they were pulse-jet-powered with a warhead of 850 kg of explosives. Over 9500 were launched at London, and many were shot down by artillery and the RAF. Over the period considered the total number of bombs within the area was 537.
It was asserted that the bombs tended to be grouped in clusters. However, a basic Poisson analysis shows this is not the case. Their guidance system being rather primitive, the data is consistent with a Poisson distribution (random).
Compared to Clarke (1946), the more modern analysis of Shaw and Shaw (2019). shows a higher density of hits in south London, hence the distribution is not really uniform over the entire region.
Clarke, R. D. (1946). An application of the Poisson distribution. Journal of the Institute of Actuaries, 72(3), 481.
Shaw, L. P. and Shaw, L. F. (2019). The flying bomb and the actuary. Significance, 16(5): 12–17.
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V1 mean(with(V1, rep(hits, times = ofreq))) var(with(V1, rep(hits, times = ofreq))) sum(with(V1, rep(hits, times = ofreq))) ## Not run: barplot(with(V1, ofreq), names.arg = as.character(with(V1, hits)), main = "London V1 buzz bomb hits", col = "lightblue", las = 1, ylab = "Frequency", xlab = "Hits") ## End(Not run)
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